Determination of the presence of certain fetal restricted antigens in vaginal and cervical samples has proved useful for verifying pregnancy, detecting ectopic pregnancy, detecting increased risk of preterm labor, or detecting rupture of the amniotic membrane. These methods are the subject of commonly assigned copending applications, Ser. Nos. 121,895, 121,900, 121,893 and 121,899, all filed Nov. 17, 1987 and commonly assigned application U.S. Ser. No. 244969 filed concurrently herewith, the disclosures of all of these applications being hereby incorporated by reference.
In these methods a sample is removed from an area within the vaginal cavity, such as the posterior fornix, cervical canal or uterine cavity, and the sample is examined to determine the presence or quantity of a fetal restricted antigen component, usually a protein such as fetal fibronectin, in the sample. The sample is removed with a swab, aspirator, suction device, lavage or the like and transferred to a suitable container for storage and transport to the testing laboratory. We have discovered that sensitive proteins such as fetal fibronectin are unstable in the sampled composition, and the protein analyte level declines during storage and transport, limiting the sensitivity of the testing methods.